Systems and methods of sensing audio with a MEMS microphone that modulates a frequency of a phase-locked loop. The MEMS microphone includes a movable electrode and a stationary electrode. The phase-locked loop includes a voltage-controlled oscillator and a phase detector. The voltage-controlled oscillator includes a biasing circuit and a plurality of inverters. The biasing circuit is configured to generate a biasing signal based on a control signal. The plurality of inverters are configured to generate an oscillating signal based on the control signal and a capacitance between the movable electrode and the stationary electrode. The phase detector is configured to detect a phase difference between the oscillating signal and a reference signal. The phase detector is also configured to generate the control signal based on the phase difference. The controller is configured to determine an audio signal based on the control signal.